BPEL process & correlation, example?

I am searching for an example BPEL project using CorrelationSets.

Can someone provide me an example, in order to help me more quickly gaining understanding of how to configure it correctly?

I have a Web service exposed in SonicESB, trying to call it from a BPEL process using an Invoke activity, and get the error

<?xml version = '1.0' encoding = 'UTF-8' ?><eventDetails xmlns="http://www.parasoft.com/bpel/audit">
   <correlationViolation xmlns="http://docs.oasis-open.org/wsbpel/2.0/process/executable">
     <correlationViolation xmlns="http://docs.oasis-open.org/wsbpel/2.0/process/executable">Message does not correspond to a start activity - GetSupplier_1</correlationViolation>
     <stackTrace>com.parasoft.bpel.engine.BpelFault: Message does not correspond to a start activity - GetSupplier_1
     at com.parasoft.bpel.engine.ProcessManager.createNewProcess(ProcessManager.java:1682)
     at com.parasoft.bpel.engine.ProcessManager.getProcess(ProcessManager.java:1860)
     at com.parasoft.bpel.engine.ProcessManager.processMessage(ProcessManager.java:2334)
     at com.parasoft.bpel.engine.MessagingUtil$2.transmit(MessagingUtil.java:486)
     at com.parasoft.bpel.engine.TransmissionThread.run(TransmissionThread.java:40)
</stackTrace>
   </correlationViolation>

</eventDetails>

Searching the Sonic knowledge base, learns to use CorrelationSets.

Thanks
Koen van den Dool